Control system for electric current rectifiers



July25, 1933. E. KERN 1,919,890

CONTROL SYSTEM FOR ELECTRIC CURRENT RECTIFIERS Filed Aug. 19, 1930 Fly 3Eve/liar Ermh Kern Attorney i UNITED {STA E Patented July 25,1933

PA ENT I E SWITZERLAND Enwm KERN, or; warm menu, SWITZERLAND, ASSIGNOR"r0 AKTIENGESELLSGHAFT wnnowmnovnnre cm, or BADEN, SWITZERLAND, Aaonvns'rocx COMPANY on dmmps mmroa ELECTRIC eel-mam nncrna'mnsApplication tied Au u pia 193e, Serial No. 476,338, and enemy Angust as,1929. l

The invention relates to improvements in control systems for electriccurrent rectifiers of the type employing an electric arc flowlng througha va o having a valveaction thereon and, particularly, to acontrolsystem in a whichfthe flowfof the arc 'iscontrolled by grdswhichinay beeither positively or negatively charged. 1 I 1 Electriccurrent rectifying structures and systems employing; controllable gridsare a. known but 1 such systems generally require an auxiliary directcurrent sourceto charge the grids at the 1 potential desired. Suchauxiliary direct current sources undes rably "complicate thesystem andfurnish an addltionalpoint" at which failure of the system may occur.JIthas been found however that a various metallic portionsa'rr'anged ininsu lated relation in the "arc' pathwithin the rectifierfduringthepaSSage ofthe are therethrough; take on a, potential intermediatethatf of the an'odes, andthat of thecathode; SuchmetallicYportions may,therefore, be

used as sources of direct current to charge the control grids withapositive'potential thereby avoiding the use of an aux llary directcurrent source for that purpose): It is; therefore, among the objects ofthe present invention to provide an electric current rectifier controlsystem in which the potential impressed on the control grids is takenfrom afn etallic portion arranged thin the rectifie V i Another obj ectof the invention is, to 1 pr 'vide anelectric current rectifying controlsystem'in'which the potential impressed on 1 the control grids is takenfrom a metallic structural portion of the rectifier in contact Withtheaccompanying description in which t Figure 1 diagrammaticallyillustrates one embod ment of the present inventlon 1n which auxiliaryanodes andgrids form the a source of supply 'of'thepotential requiredfor A controlling the main rectifying arc,

FigureQ diagrammatically illustrates one auxiliary rectifier itselfis'used inbdification of the structure shown-"in Fig. 1 in whichmodification the control, poten tial is produced inra' device separatefrom the main rectifier, and

Figure3 diagrammaticallyillustrates n further modificatiomof the systemin which thesupply grids showninFigs. 1 and-2 are eliminated and themetallic *tank of the tifier which, as diagrammatically indicated r 1nthe drawing-,may be of the metallic casing type, having-a plurality ofmain anodes 6 and a cathode 7 of suitable vaporizable material, such asmercury, having a valve action on an electric arc flowing between theanodes andthe cathode. The anodes each have a control grid 8 arranged'between the anode and the cathode on which gridsthe potential requiredfor controlling the action of the main arc is impressed. i

V The potential suppliedto the'control grids a 8 is supplied fromgrids19 arranged adjacent the auxiliary or excitation anodes '11 to whichcurrent is supplied from-a transformer 12. The supply grids 9 are inthepath of the arc flowing from theexcitatio'n anodes 11 to the cathode andoutof the V path of the arc flowing from the main anodes 6 :to thecathode.- Thesupply grids 9 are connectedwith the control grids S-bymeans of a resistance and a reversing switch. As shown in Fig. 1 of thedrawing the poten-' tial suppliedtov the control grids 8 from supplygrids 9 is positive and islimited by the resistance 13. The switch ltmay.a

however be reversed to connect thecontrol grids 8 through anohmicresistance 16 and 1 an excitation current limiting resistan'celfi, withthe cathode 7 and the neutral point of the transformer 12 to obtain anegative potential with respect to the anodes'whenever such becomesnecessary forpropercon trol of the rectifying action. The arc'flowingbetween the excitation anodesell and the cathode '7 impresses a positive1ootential on the supply grids 9.-

The value of such posi- URL) as the contive control potential may beadjusted by enclosing or shielding the auxiliary arc from the main arc.The control system is preterably formed as a multiphase system so thatthe supply grids 9, which are conductively connected, are atsubstantially a constant positive potential relative to that of thecathode.

The control potential may also be produced in a device separate from thework circuit which is supplied by the rectifier, as shown in Fig. 2, inwhich the transformer 12 supplies current to a plurality of anodes 21,22 and'23 arnnged in a separate rectifier 24 having a cathode 26connected with the cathode 7 of the main rectifier 4. The arc flowing inthe auxiliary rectifier 24 impresses a positive potential on the supplygrids 27, 28 and 29 which may then be supplied to the control grids 8over resistances 13 and reversing switch 14 as above described. Theoperation of switch 14 to its alternate position will, however, connectthe control grids 8 with the cathode 7 through current limitingresistances 16, 17 and thereby impress a potential negative with respectto the anodes 6 on the control grids 8 as in the embodiment according toFigure 1 of the drawing. In this modification of the system, the controlpositive potential is thus produced in a device separated from the mainrectifier and disturbances in one will be without eflect on the other.The potential impressed on the supply grids can also be more accuratelycontrolled than if both supply and control grids are present in the samestructure.

As illustrated in Fig. 3, the metallic tank itself of the auxiliaryrectifier 24 above mentioned is used as the source of control positivepotential thereby avoiding all useof the supply grids. As explained withreference to Figures 1 and 2 of the drawing the movement of switch 14 toits alternate position operates to impress a potential on the controlgrids 8 negative with respect to the associated anodes 6. The advantagesof the present construction are that the insulated grids and theinsulating bushings for the conductors leading to the grids areeliminated thereby materially simplifying and cheapening theconstruction.

It will'thus be seen that the present invention provides a controlsystem for electric current rectifiers in which the use of an auxiliarydirectcurrent source of p0tential is avoided and portions oftherectifying structure itself are used to supply the control potentialto the control grids thereof. Either a positive or a negative potentialmay be obtained as desired by a simple and inexpensive means and thevalue of such potential may be regulated as may appear to be necessary.

Although but a few embodiments of the present invention have beenillustrated and described, it will be apparent to those skilled in theart that various changes and modifications may be made therein withoutdeparting from the spirit of the invention or from the scope of theappended claims.

The invention claimed is:

1. In an electric current rectifier control system, an electric currentrecetifier comprising a tank, a cathode within said tank, anodesextending into said tank, control grids arranged adjacent said anodes,and means arranged in the path of an are other than the arc flowing fromsaid anodes to said cathode operative to supply a potential to saidgrids for controlling the rectifying action. I

2. In an electric current rectifier control system, an electric currentrectifier comprising a tank, a cathode within said tank,

anodes extending into said tank, control grids arranged adjacent saidanodes, means for producing an electric arc auxiliary to that flowingbetween said anodes and said cathode, and means arranged in the path ofthe. auxiliary arc operative to supply a positive control potential tosaid control grids.

3. In an electriccurrent rectifier control system, an electric currentrectifier comprislng a tank, a cathode within said tank, main anodesextending into said tank, control grids arranged adjacent said mainanodes, anodes for producing an electric arc auxiliary to that flowingbetween said main anodes and said cathode, grids arranged in the path ofthe auxiliary arc to receive a positive potential, and means forconnecting said supply grids and said control grids to govern the flowofcurrent from said main anodes to said cathode.

4. In a control system for electric current rectifiers of the arc type,an electric current rectifier, means for producing an operating arewithin said rectifier, means for producing an auxiliary arc within saidrectifier, 1

means in the path of the operating are for receiving a potential tocontrol the same, and means in the path of the auxiliary arc forsupplying a potential to said operating H arc controlling means.

5. In a control system for electric current rectifiers of the arc type,an electric current rectifier having anodes and a cathode, grids forcontrolling the arc flowing between the anodes and the cathode, meansfor producing an auxiliary arc within said rectifier, grids in the pathof the auxiliary arc to-receive a potential, and means connecting saidcontrol grids and said last mentioned grids.

6. In a control system for electric current rectifiers of the arc type,an electric current rectifier having anodes and a cathode, grids forcontrolling the arc flowing between the anodes and the cathode, anauxiliary current rectifier having anodes and a cathode, gridsarrangedin said auxiliary recti fier :to receive a potential thereon, and

means connecting said grids of said fmain, rectifier wlth said grids ofsald auxlhary rectifier to controlthe are within said main rectifier.

7 In a controlisystem for electric current rectifiers of the 'arc' type,a main electric current rectifier'having anodes and a cathode, grids.for controlling the arc flovvingj between the anodes and the cathode; anauxiliary electric current rectifier having main rectifier and saidauxiliary rectifier t0 anodes and a cathode, grids arranged in saidauxiliary rectifier to receive a potential, and

means for connecting said grids of said supply a positive potential, tothe gridsof:

the former,

8. In a controlsystem for electriccurrent rectifiers, in combination, amain electric current "rectifier of the metallic vapor arcing typehaving a cathode anda plurality. of anodes constitutingelectrodes forthe flow of arcs therebetween, grids arrangedaadjacent said anodes forcontrolling 831d, arcs,

an auxiliary electric current rectifier comprising a cathode and aplurality of anodes V supportedvvithin an electrically conductive casingin insulated relation therewith, the last said cathode and anodesconstituting electrodes for the flow'of arcs therebetween v said casingwith the first said press said potentials thereon.

:ERWIN KERN. V

